Assessing the risk of central post-stroke pain of thalamic origin by lesion mapping.

Central post-stroke pain of thalamic origin is an extremely distressing and often refractory disorder. There are no well-established predictors for pain development after thalamic stroke, and the role of different thalamic nuclei is unclear. Here, we used structural magnetic resonance imaging to identify the thalamic nuclei, specifically implicated in the generation of central post-stroke pain of thalamic origin. Lesions of 10 patients with central post-stroke pain of thalamic origin and 10 control patients with thalamic strokes without pain were identified as volumes of interest on magnetic resonance imaging data. Non-linear deformations were estimated to match each image with a high-resolution template and were applied to each volume of interest. By using a digital atlas of the thalamus, we elucidated the involvement of different nuclei with respect to each lesion. Patient and control volumes of interest were summed separately to identify unique areas of involvement. Voxelwise odds ratio maps were calculated to localize the anatomical site where lesions put patients at risk of developing central post-stroke pain of thalamic origin. In the patients with pain, mainly lateral and posterior thalamic nuclei were affected, whereas a more anterior-medial lesion pattern was evident in the controls. The lesions of 9 of 10 pain patients overlapped at the border of the ventral posterior nucleus and the pulvinar, coinciding with the ventrocaudalis portae nucleus. The lesions of this area showed an odds ratio of 81 in favour of developing thalamic pain. The high odds ratio at the ventral posterior nucleus-pulvinar border zone indicates that this area is crucial in the pathogenesis of thalamic pain and demonstrates the feasibility of identifying patients at risk of developing central post-stroke pain of thalamic origin early after thalamic insults. This provides a basis for pre-emptive treatment studies.

A case-control study on cortical thickness in episodic cluster headache.

OBJECTIVE: This study aims at investigating cortical thickness in cluster headache patients as compared with a healthy control group. BACKGROUND: The pathobiology of cluster headache is not yet fully understood, although a dysfunction of the hypothalamus has been suggested to be causal. Previous studies in migraine and trigeminal neuropathic pain have demonstrated changes in cortical thickness using cortex segmentation techniques, but no data have been published on cluster headache. METHODS: We investigated 12 men with episodic cluster headache during a phase without acute headache as well as age and sex-matched healthy controls using high resolution T1-weighted magnetic resonance imaging acquired at 3T and performed a categorical whole-brain surface-based comparison of cortical thickness between groups. Furthermore, a correlation analysis of disease duration and cortical thickness was conducted. RESULTS: In comparison with control subjects, we found a reduction of cortical thickness in the angular gyrus and the precentral gyrus in cluster headache patients contralaterally to the headache side. These reductions did not correlate with disease duration. The cortical thickness of an area within the primary sensory cortex correlated with disease duration. CONCLUSIONS: This study demonstrates alterations in cortical thickness in cluster headache patients suggesting a potential role of cortical structures in cluster headache pathogenesis. However, it cannot be determined from this study whether the changes are cause or consequence of the disorder. The correlation of cortical thickness with disease duration in the somatosensory cortex may suggest disease-related plasticity in the somatosensory system.

Systemic thrombolysis in ischemic stroke after recent oral surgery and management of oral cavity bleeding.

Thrombolysis with recombinant tissue plasminogen activator in the treatment of acute ischemic stroke carries a long list of contraindications. One of these is recent surgery, but the extent of complications after minor surgeries such as dental extraction or oral surgical procedures is unclear. Here, we report the management of 2 cases with accidental bleeding from the oral cavity during systemic thrombolysis in ischemic stroke because of recent unreported oral surgery. Bleeding at the operation site occurred early and was stopped by prompt discontinuation of the recombinant tissue plasminogen activator infusion and local compressive therapy. Patients and relatives may not be aware that surgical procedures within the oral cavity are regarded as minor surgery and should be explicitly asked during the evaluation of ischemic stroke within the period for thrombolysis.

Utility of diffusion tensor-imaged (DTI) motor fiber tracking for the resection of intracranial tumors near the corticospinal tract.

PURPOSE: Treatment of intracranial tumors near the corticospinal tract remains a surgical challenge. Several technical tools to map and monitor the motor tract have been implemented. The present study aimed to assess the utility of diffusion tensor imaging (DTI) fiber tracking in the surgical treatment of motor eloquent tumors at our institution. METHODS: Patients operated for intracranial tumors close to the motor tract with the use of intraoperative image guidance including DTI fiber tracking of the corticospinal tract and intraoperative motor evoked potential (MEP) monitoring were analyzed. The intraoperative utility of fiber tracking data was analyzed. Furthermore, preoperative MRI scans with and without motor fiber tracking were reevaluated post hoc for tumor relation to the motor tract, estimated resectability, and best approach. Thereby, the utility of fiber tracking in surgical planning was assessed. RESULTS: Nineteen patients were analyzed. The estimation of tumor localization in relation to the motor tract and of resectability was not influenced by fiber tracking in any of the cases. Only in one single case did evaluating surgeons change their surgical approach after the addition of the fiber tracking data. In all cases, fiber tracking included in image guidance did not change the intraoperative strategy, while MEP monitoring did. CONCLUSIONS: DTI fiber tracking did not influence the surgical planning or the intraoperative course. However, it is still used at our institution due to its ease in acquisition and its potential impact in a larger series. Furthermore, more experience with this technique is required to lead to a technical improvement.

Labeling of human neural precursor cells using ferromagnetic nanoparticles.

Fetal human neural precursor cells (NPCs) are unique with respect to their capacity to proliferate and to preserve their potential to differentiate into neurons and glia. Human mesencephalic neural precursor cells (hmNPCs) provide a source for dopaminergic neurons. Preclinical and clinical research will benefit from reliable in vivo tracking of transplanted cells. Here, we investigate the potency of very small superparamagnetic iron oxide particles (VSOPs) to label hmNPCs, the effect of VSOPs on survival, proliferation, and differentiation of hmNPCs, and the sensitivity of 1.5T magnetic resonance imaging (MRI) to detect labeled cells in living rats following transplantation. When incubated with VSOPs at 1.5 mM, >95% of hmNPCs incorporated VSOPs without detectable impact on cell viability (>90%) or proliferative capacity, as measured by the expression of proliferating cell nuclear antigen (PCNA) and cell cycle distribution. Labeled hmNPCs differentiate into neurons (>30%) and glia with no detectable difference compared to nonlabeled cells. Following transplantation into rat striata, marked paramagnetic signal changes were detected for as long as three months postsurgery using MRI, corresponding to the histologically-identified graft. Our data indicate that hmNPCs can be labeled with VSOPs without impairment of viability, proliferation, or multipotency. Labeled, transplanted cells are detectable in vivo using 1.5T MRI.

Cerebral processing of auditory stimuli in patients with irritable bowel syndrome.

AIM: To determine by brain functional magnetic resonance imaging (fMRI) whether cerebral processing of non-visceral stimuli is altered in irritable bowel syndrome (IBS) patients compared with healthy subjects. To circumvent spinal viscerosomatic convergence mechanisms, we used auditory stimulation, and to identify a possible influence of psychological factors the stimuli differed in their emotional quality. METHODS: In 8 IBS patients and 8 controls, fMRI measurements were performed using a block design of 4 auditory stimuli of different emotional quality (pleasant sounds of chimes, unpleasant peep (2000 Hz), neutral words, and emotional words). A gradient echo T2*-weighted sequence was used for the functional scans. Statistical maps were constructed using the general linear model. RESULTS: To emotional auditory stimuli, IBS patients relative to controls responded with stronger deactivations in a greater variety of emotional processing regions, while the response patterns, unlike in controls, did not differentiate between distressing or pleasant sounds. To neutral auditory stimuli, by contrast, only IBS patients responded with large significant activations. CONCLUSION: Altered cerebral response patterns to auditory stimuli in emotional stimulus-processing regions suggest that altered sensory processing in IBS may not be specific for visceral sensation, but might reflect generalized changes in emotional sensitivity and affective reactivity, possibly associated with the psychological comorbidity often found in IBS patients.

Cortical distribution of speech and language errors investigated by visual object naming and navigated transcranial magnetic stimulation.

Navigated transcranial magnetic stimulation (nTMS) gains increasing importance in presurgical language mapping. Although bipolar direct cortical stimulation (DCS) is regarded as the gold standard for intraoperative mapping of language-related areas, it cannot be used to map the healthy human brain due to its invasive character. Therefore, the present study employed a non-invasive virtual-lesion modality to provide a causality-confirmed cortical language map of the healthy human brain by repetitive nTMS (rTMS) with functional specifications beyond language-positive/language-negative distinction. Fifty right-handed healthy volunteers underwent rTMS language mapping of the left hemisphere combined with an object-naming task. The induced errors were categorized and frequency maps were calculated. Moreover, a principal component analysis (PCA) was performed on the basis of language-positive cortical regions for each error category. The left hemisphere was stimulated at 258-789 sites (median: 361.5 sites), and 12-241 naming errors (median: 72.5 errors) were observed. In male subjects, a total number of 2091 language errors were elicited by 9579 stimulation trains, which is equal to an error rate of 21.8 %. Within females, 10,238 stimulation trains elicited 2032 language errors (19.8 %). PCA revealed that the inferior parietal lobe (IPL) and middle frontal gyrus (MFG) were causally involved in object naming as a semantic center and an executive control center. For the first time, this study provides causality-based data and a model that approximates the distribution of language-related cortical areas grouped for different functional aspects of single-word production processes by PCA.

Functional language shift to the right hemisphere in patients with language-eloquent brain tumors.

OBJECTIVES: Language function is mainly located within the left hemisphere of the brain, especially in right-handed subjects. However, functional MRI (fMRI) has demonstrated changes of language organization in patients with left-sided perisylvian lesions to the right hemisphere. Because intracerebral lesions can impair fMRI, this study was designed to investigate human language plasticity with a virtual lesion model using repetitive navigated transcranial magnetic stimulation (rTMS). EXPERIMENTAL DESIGN: Fifteen patients with lesions of left-sided language-eloquent brain areas and 50 healthy and purely right-handed participants underwent bilateral rTMS language mapping via an object-naming task. All patients were proven to have left-sided language function during awake surgery. The rTMS-induced language errors were categorized into 6 different error types. The error ratio (induced errors/number of stimulations) was determined for each brain region on both hemispheres. A hemispheric dominance ratio was then defined for each region as the quotient of the error ratio (left/right) of the corresponding area of both hemispheres (ratio >1 = left dominant; ratio <1 = right dominant). RESULTS: Patients with language-eloquent lesions showed a statistically significantly lower ratio than healthy participants concerning "all errors" and "all errors without hesitations", which indicates a higher participation of the right hemisphere in language function. Yet, there was no cortical region with pronounced difference in language dominance compared to the whole hemisphere. CONCLUSIONS: This is the first study that shows by means of an anatomically accurate virtual lesion model that a shift of language function to the non-dominant hemisphere can occur.

Utility of presurgical navigated transcranial magnetic brain stimulation for the resection of tumors in eloquent motor areas.

OBJECT: Navigated transcranial magnetic stimulation (nTMS) is a newly evolving technique. Despite its supposed purpose (for example, preoperative central region mapping), little is known about its accuracy compared with established modalities like direct cortical stimulation (DCS) and functional MR (fMR) imaging. Against this background, the authors performed the current study to compare the accuracy of nTMS with DCS and fMR imaging. METHODS: Fourteen patients with tumors in or close to the precentral gyrus were examined using nTMS for motor cortex mapping, as were 12 patients with lesions in the subcortical white matter motor tract. Moreover, preoperative fMR imaging and intraoperative mapping of the motor cortex were performed via DCS, and the outlining of the motor cortex was compared. RESULTS: In the 14 cases of lesions affecting the precentral gyrus, the primary motor cortex as outlined by nTMS correlated well with that delineated by intraoperative DCS mapping, with a deviation of 4.4 ± 3.4 mm between the two methods. In comparing nTMS with fMR imaging, the deviation between the two methods was much larger: 9.8 ± 8.5 mm for the upper extremity and 14.7 ± 12.4 mm for the lower extremity. In 13 of 14 cases, the surgeon admitted easier identification of the central region because of nTMS. The procedure had a subjectively positive influence on the operative results in 5 cases and was responsible for a changed resection strategy in 2 cases. One of 26 patients experienced nTMS as unpleasant; none found it painful. CONCLUSIONS: Navigated TMS correlates well with DCS as a gold standard despite factors that are supposed to contribute to the inaccuracy of nTMS. Moreover, surgeons have found nTMS to be an additional and helpful modality during the resection of tumors affecting eloquent motor areas, as well as during preoperative planning.